Most organisms respond to stimuli in their environment by movement (taxis) toward or away from the stimulus; yet the molecular mechanism of taxis is poorly understood in any organism. The research proposed here will explore bacterial behavior, especially chemotaxis (movement toward or away from chemicals) in Bacillus subtilis and phototaxis (movement toward light) and chemotaxis in Rhodospirillum rubrum. The ultimate objective is to describe the behavior in molecular terms. More immediately, we ask such questions as the following: What is the mechanism by which information is transmitted from receptors to flagella? How do receptors--photoreceptors or chemoreceptors--generate this signal? The immediate experimental objectives of work for this coming year are the following: 1) determine repertoire of attractants and repellants and specificities of receptors in Bacillus subtilis; 2) isolate and characterize mutants in chemotaxis and transport of attractants; 3) study effects of uncouplers of oxidative phosphorylation and inhibitors of electron transport in Bacillus subtilis since we have found them to be repellents; 4) determine role of ions, such as Ca,ions in motility and chemotaxis in Bacillus subtilis; 5) develop light trap assay for phototaxis in Rhodospirillum rubrum and obtain and characterize mutants in phototaxis and photosynthesis.